its probably popular because of the price of eggs nowadays, not to mention the eggs are organic free range.
chickens eat just about anything, you could feed them on food scraps and still get eggs, you dont have to buy them pellets. I do because it gives them their full balanced diet.
i suppose if you cooked a lot of vegetable stew, soups, pasta, you could easily feed them on scraps.
So £15 Per chicken = £60
Food Scraps = £0
4 Eggs per day roughly, they soon pay for themselves.